This invention relates to document feeder and delivery systems and, more particularly, to vacuum systems which are adapted to tolerate a greater degree of document misalignment, document thickness variations, document size intermix, and surface non-uniformity, than was heretofore possible and to reduce the wear and tear on vacuum cups used to pick up the documents.
The inventive document feeder and delivery system uses vacuum cups designed to pick up one document at a time and to deliver it to a document transport and processing machine. A horizontal stack of vertically oriented envelopes is exemplary of the arrangements and types of documents which are likely to be handled by the inventive document feeder. A postage scale and metering machine is exemplary of a document-processing machine which is likely to be fed by the inventive document feeder system. However, the invention is not necessarily limited to feeding envelopes or to any other specific document form.
The envelopes are stacked on an edge, and the stack is placed horizontally on a belt. The belt moves the envelopes into the reach of the vacuum cups. The vacuum cups pivot on a circular arc toward the exposed end of the stack of envelopes. The pivot point of the vacuum cup arc is located below the envelope. On each cycle, the vacuum cups grasp one of the envelopes and then positions it within the grasp of a document transport system. The transport system carries the envelope away while the vacuum cups go back to get the next envelope.
In prior feeding systems, the vacuum cups would withdraw an envelope from the stack, remove the vacuum, and drop the envelope onto a second moving belt located below the stack. Furthermore, no provision was made for envelopes presented at a skewed angle or for an intermix of envelopes having varying thicknesses. This type of system had five common problems. The envelopes drop from the cups because they are accelerated by the force of gravity. The time required for the envelope to fall, limits the cycle speed of the machine. At higher speeds, the vacuum cups drop an envelope and return fast enough to impact the same envelope. This impact abrades the cups and shortens their life. The envelopes are not positively positioned into the document transport and, at times, hang up on the second moving belt and never reach the transport system. A vacuum cup depends, at least in part, upon its being seated squarely upon the envelope. Therefore, if the envelope is presented to the cups at a skewed angle, the vacuum may not be properly formed. This increases the expense and complexity of the envelope registration system. Finally, there was not any provision for manipulating the vacuum cups to aid in separation of adjacent documents.
Some of these problems were overcome by Applicant's assignee in copending application Ser. No. 148,068 filed May 12, 1980 entitled VACUUM DOCUMENT FEEDER now U.S. Pat. No. 4,346,876. This copending application was an improvement over prior designs but Applicant was able to improve further over this device. The device in the '068 disclosure did not always provide for singular pick off of the envelope from the stack. This was due to vacuum bleed through tending to hold together two relatively thin envelopes. Also, a static charge between envelopes tended to keep adjacent envelopes together. Furthermore, when one envelope is pulled away from a second envelope in a perpendicular plane from the first, air pressure tends to suck the second envelope along with the first.
Accordingly, an object of the invention is to provide new and improved vacuum envelope feeders. Here, an object is to provide a vacuum cup support mechanism which follows a path that eliminates the above-stated disadvantages. In this connection, an object is to provide a low-cost mechanism which accomplishes the foregoing and other objects, in new and improved ways.
An additional object is to provide a document feeder to reliably separate and feed an intermix of media varying in length, height, and thickness. It is also an object to provide vacuum cup path that traces a route such that the cup clears the fed document on its return stroke to pick off the next document. A further object is to provide a feeder which presents documents to the vacuum cups in a constant orientation and with minimum inter-document force.
A related object is to provide a document feeder which allows the pick off mechanism to remove only the first envelope from a stack of envelopes without also pulling a second adjacent envelope from the stack.
In keeping with an aspect of the invention, the foregoing and other objects are accomplished by a four-bar linkage or lever arm system which moves a table over a somewhat crescent-shaped coupler curve, while at all times holding an edge of that table parallel to the envelopes. At least two vacuum cups are pivotally mounted on the table to tilt at an angle which is large enough to accommodate poorly registered envelopes. The vacuum cups pivot in such a manner that they cause the lead envelope to buckle aiding in separation of the lead envelope from the stack. A cam on a drive wheel associated with the four-bar linkage coordinates the table movement with the vacuumizing of the cups. The pivoting of the cups is accomplished by a cam follower system driven by a universal drive system.